Electric furnace.



W. G. CLARK. ELECTRIC PURNACE.

APPLICATION FILED DEC. 17,1906.

2 SHEETS-SHEET l PATEN'IED SEPT. 3, 1907.

N 865 o16. o W. G. CLARK.

ELECTRIC FURNAGE. APPLIUATION FILED DB0.17,1906.

PATENTED SEPT. 3, 190'?.

2 SHEETS-SHEET 2.

Figf' A TTORNEY.

Y or electrode is highly incandescent.

' easily.

UNITED STATES PATENT OFFICE.

WALTER Gr. CLARK, OF NEW YORK, N. Y., ASSIGNOR TO ELECTRIC FURNACE COMPANY, OF PORTLAND7 MAINE, A CORPORATION OF MAINE.

ELECTRIC FURNACE.

Specification of Letters llatent.v

Patented sept. s, 1907.

Application led December 17,1906. Serial No. 348,331.

and Improved Electric Furnace, of which the following is a full, clear, and exactV description.

p My invention relates to improvements in lelectric furnaces, and more especially electric furnaces of the incandescent type as distinguished from the arc type of furnaces. i

Heretofore it has been common in incandescent electric furnaces to heat the furnace by passing a current of electricity through the furnace walls, but to get the furnace toa sufficiently high heat foi` melting purposes, such a system causes the furnace to be rapidly burned out and otherwise injured by the excessive current. Another common way of heating electric furnaces is to make the furnace walls of resisting but conducting materials, and use an electrode or heater, which is also a resistance conductor, and which extends downward into the material to be melted, or in the Abath or slag, but in such cases the circuit is completed through the bath or slag, andthe furnace is for this reason more or less inelcient, andespecially as during the first melting processes short circuits are likely to occur which greatly interfere with the working of the furnace.

The object of my invention is\to do away with the above difficulties, and,.1 do this by providing a central electrode or electrodes, which electrode is shaped to fit the furnace bottom, andvwhich for `the greater part of its length is of higher resistance than its foot and than the furnace walls, so that the walls of the furnace are comparatively cool, While the' central heater To facilitate melting I have the central heater or electrode constructed so that it can be removed slightly from the furnace bottom when the workl is started, and so a series of arcs will be sprung between the foot of the central heater and the furnace Wall, and thiscauses the material around the foot to be immediately melted, and then the foot can be dropped back against the wall, and as the melting is already started it will continue A further object of my invention is to provide a convenient, economic means of regulating the furnace feed so that the, material to beunelted can be heated and melted, or partially melted as it passes inward to the furnace. All this to the end that the heat generated by the current can be utilized-to the best adyantage, and by radiating itichiey from'the center, it is usable for melting purposes, whereas with the walls heated to a high state of incandescence, more heat is wasted than is actually utilized.

With these ends in View, my linvention consists of `pecially the harder kinds of glass.

an electric furnace, the construction and operation of which will be hereinafter clearly described and the novelfeatures claimed.

Reference is to be had to the accompanying drawings forming a part of this specification, in which similar figures of reference indicate corresponding parts in al the views.

Figure 1 is a Vertical section of a furnace embodying my invention, and shows an open hearth type of furnace which is well adapted to melting glass,l and es- Fig. 2 shows in vertical section a furnace which can be used for melting purposes, and which has means for raising and lowering the central heater or electrode, and Fig. 3 is a vertical'rsection of a type of furnace which is well adapted for use in melting quartz or other material requiring a high temperature. v

The furnace 10 can be of any suitable shape, but I prefer to give it a rounded bottom, and it is constructed with an open hearth 11, into which an operator may dip to remove the melted material as itis needed. The material of the furnace is such as to withstand the action of the current and of the melted material, and I find graphite is perhaps the best material for this purpose, especially as in my type of furnace the furnace Wall is of comparatively low resistance, and the relatively pure graphite is better for this reason than it is to have the graphite -mixed with fire clay or other material of higher electrical resistance. a

For the glass furnace andfor melting many other things, I prefer the type shown in Fig. 1, and here a feed chute or pocket 12 of'the same material "asl the furnace 10 is arranged in the upper part of the furnace, and it has an opening therethrough in which fits loosely the central heater or electrode 13, and this can be reduced in cross section through its central and lower part as shown at 13?, to make this part of higher resistance so that the heating at this point will be more quickly accomplished. The electrode or heater 13 terminates in the'foot 14 which is of larger cross section than any other part of .the electrode, and which is preferably rounded on the bottom soas to fit snugly against th'e furnace bottom. It will be seen that the sand or other material which is fed into the pocket l2 will be melted by the heat from the wall of the pocket, and more especiallyfrom the electrode 13, and will drop down into the furnace bottom and can be removed when sucientlyliquid from the hearth 11. To start the action-the foot 14 can be raised slightly so as to spring arcs between itself and the furnace wall, thus melting a little ofthe material very quickly, after which the foot can be dropped back into place. Of course Athis could be done even though the bottom electrode or heater,` 'but in such case the arc being concentrated would have a tendency to destroy lquickly the furnace bottom. i

The electrical connections can be made in any convenient way, as for instance I have shown the electrode 13 provided with a metal strap l5, which connects with a leading-in Wire a, while the furnace Wall is provided with a strap 17 which connects'with a suitable conductor 16, and this connects with a second leading-in wire al,

In Fig. 2 I have shown a furnace substantially as described,` but have illustrated a simple means of raising and lowering the heater or electrode 13. As here shown, the ring 15 connects by means of a tongue 18 with the collar 19 on the shaft 20, and thelatter has i a crank connection with the wheels 21 of the shait 22,

so that when the shaft is rotated the wheels are turned and the part 13 can be raised or lowered. I have shown this means of raising and lowering the electrode inmere outline, as obviously any usual mechanical contrivance for raising andrlowering objects can be used, and I do not claim the mechanism itself.

In Fig. 3 I have shown the furnace arranged at an inclination so that when heated one can dip down into it easily, and in either type of `furnace the electrodelor heater can have some suitable means for raising and lowering it.` 'Ihel furnace 10IL shown in Fig. `3 has an opening in the side' near the bottom which can be closed by a cover 23, and the latter can be removed and the material dipped out in a liquid state from the hottestpart of the furnace. This type of furnace is better adapted for melting quartz or other material requiring 'a relatively high temperature. It will be understood, of course, that in either type of furnace I can use a plurality of the internal resistance heaters or electrodes, instead of one, this depending on the size of the furnace.

esame From the foregoing description it will be seen that the furnace which I have described is a very simple and inexpensive one, that a very high heat can' be maintained in it, and especially that the heat and current are economized.

' Having thus fully described my invention', I claim as new and desire to secure by Letters Patent:-

- 1. An electric furnace having its walls of conducting material of relatively low resistance, and an internal heateror electrode arranged to Contact at its lower end with the furnace walls, and being of less resistance at its end portions thun :1t its intermediate portions und means for elevating the electrode. y

2. An electric furnace having its walls of relatively low electrical resistance, and an internal electrode or heater' of relatively high electrical resistance, the said internal heater having its lower end arranged to Contact with the furnace wall, and being of higher resistance above its lower end than at the said extreme lower portion and means for elevatingr the electrode.

3. An electric furnace having a wall of relatively low electrical resistance and an internal 'heater or electrode of relatively high resistance, the internal heater or electrode having a foot piece of less resistance than its body portion, and having said foot piece shaped to fit snugly against the furnace wail and means for elevating the electrode.

4. An electric furnace havingT its wall of relatively low electrical resistance, and having an internal electrode or heater of relatively high resistance, the said electrode being movable in and out of the furnace and having its lower end terminating in a foot piece which ftsgthe furnace bottom and means for elevating the electrode.

5. An electric furnace having its wall of relatively low resistance, and with an opening in the side thereof for the removable of material, and an internal electrode or heater of relatively Ahigh resistance, movable in and out of the furnace andf'hsving its lower end shaped to lit the furnace bottom und means for elevating the electrode.

WALTER G. CLARK.

Witnesses:

WARREN B. HUTcmNsoN, FxAuK L. STUBBS. 

